Closed-loop thermal regeneration of adsorbents containing reactive adsorbates

Abstract

A method is disclosed for the thermal regeneration of an adsorbent which contains adsorbed components which can react with and damage the adsorbent at regeneration temperatures. The method comprises passing a hot regeneration gas through a bed of the adsorbent at a sufficiently high flow rate such that the residence time and reaction of the desorbed components in the adsorbent bed are minimized. For removing water from CaX or SrX zeolites, the flow of nitrogen regeneration gas is controlled so that the nitrogen gas residence time in the bed is less than one second.

We claim: 
     
       1. A method for the thermal regeneration of an adsorbent containing one or more adsorbed reactive components which can react with and damage said adsorbent during regeneration comprising passing at a regeneration temperature a regeneration gas which is essentially free of said reactive components through a bed of said adsorbent which initially contains said adsorbed reactive components at a temperature less than said regeneration temperature whereby said adsorbed reactive components are desorbed, and withdrawing therefrom a purge effluent stream comprising desorbed reactive components and said inert regeneration gas, wherein the flow rate of said regeneration gas is controlled such that the gas residence time in said bed of adsorbent is less than about one second, whereby damage to said adsorbent by reaction with said reactive components at said regeneration temperature is minimized. 
     
     
       2. The method of claim 1 wherein said adsorbent is a bivalent ion-exchanged type A or type X zeolite. 
     
     
       3. The method of claim 2 wherein said adsorbent is a calcium-exchanged type X zeolite. 
     
     
       4. The method of claim 2 wherein said adsorbent is a strontium-exchanged type X zeolite. 
     
     
       5. The method of claim 1 wherein said regeneration temperature is between about 200° and 800° F. and said regeneration gas is nitrogen. 
     
     
       6. The method of claim 1 wherein said regeneration gas is air. 
     
     
       7. The method of claim 1 wherein less than about 10% of the adsorption capacity at ambient temperatures of a selected reversibly-adsorbed component is lost during regeneration. 
     
     
       8. The method of claim 1 wherein said desorbed reactive components comprise water. 
     
     
       9. The method of claim 8 wherein at least a portion of said water is removed from said purge effluent stream and the resulting stream is heated and recycled to said bed of adsorbent for use as said regeneration gas. 
     
     
       10. The method for claim 9 wherein said regeneration gas is passed through said bed of adsorbent until said purge effluent stream reaches a dew point of less than about -4° F. 
     
     
       11. The method of claim 9 wherein said water is removed by cooling said purge effluent stream and removing condensed water therefrom, and removing essentially all of the non-condensed water from said cooled purge effluent stream by adsorption in a cyclic adsorption system. 
     
     
       12. The method of claim 11 wherein said regeneration gas is passed through said bed of adsorbent until said purge effluent stream reaches a dew point of less than about -4° F. 
     
     
       13. The method of claim 11 wherein said cyclic adsorption system is a pressure swing adsorption system. 
     
     
       14. The method of claim 11 wherein said cyclic adsorption system is a temperature swing adsorption system. 
     
     
       15. The method of claim 14 wherein said temperature swing adsorption system contains an adsorbent selected from the group consisting of type 3A zeolite, type 4A zeolite, type 5A zeolite. NaX zeolite, high silica sodium mordenite, silica gel, activated alumina, and activated carbon. 
     
     
       16. The method of claim 14 wherein the product stream from said temperature swing adsorption system has a dew point of as low as -80° F. 
     
     
       17. The method of claim 9 wherein said water is removed from said purge effluent stream by cooling said stream and removing condensed water therefrom, compressing and cooling the resulting stream and removing additional condensed water therefrom, removing essentially all of the non-condensed water from the resulting cooled and compressed stream by a first cyclic adsorption system and reducing the pressure of the resulting stream prior to heating and recycling to said bed of adsorbent. 
     
     
       18. The method of claim 17 wherein the effluent stream from said first cyclic adsorption system is passed to a second cyclic adsorption system for the removal of additional water. 
     
     
       19. The method of claim 18 wherein said first and second cyclic adsorption systems are temperature swing adsorption systems. 
     
     
       20. The method of claim 19 wherein the adsorbents in said first and second cyclic adsorption systems are selected from the group consisting of type 3A zeolite, type 4A zeolite, type 5A zeolite, NaX zeolite, high silica sodium mordenite, silica gel, activated alumina, and activated carbon. 
     
     
       21. The method of claim 19 wherein the effluent stream from said first cyclic adsorption system has a dew point as low as -40° F. and the product stream from the second cyclic adsorption system has a dew point as low as -80° F. 
     
     
       22. The method of claim 17 wherein said second cyclic adsorption system is a pressure swing adsorption system.